Stella McCartney’s much-awaited collaboration with GapKids officially kicked off its stylish tot collection with a pop-up shop in the City of Angels. The temporary space on L.A.’s Robertson’s Boulevard brought out Hollywood’s most stylish moms yesterday including Amber Valletta, Jessica Capshaw, Jen Meyer and rock royalty Liv Tyler in a chic LBD. The designer’s pieces usually run into the more wallet-busting luxurious fare, but with this collection of pieces ranging from layette to 12 year-olds, price points are refreshingly Gap-shopper friendly.